A pneumatically actuated telescoping mast is well known in the prior art and is generally of such a nature that it may be mounted readily on the roof of a motor vehicle, such as an emergency vehicle or utility vehicle. In such arrangement the mast is generally used for positioning electrical devices, particularly lighting fixtures at an elevated point above the vehicle. The effect is to immediately light a large area above the vehicle. This allows that emergency procedures can be conducted under the light, such as at accident scenes or by utility work crews such as after a storm. Pneumatically actuated telescoping masts are particularly advantageous in such situations since they are light weight, compact in a retracted position and capable of being mounted on the roof of most emergency motor vehicles, including automobiles.
The prior art pneumatically telescoping masts are extended using air, under pressure, and in a fully extended position, are generally vertical. A pneumatic telescoping mast typically includes a compressor or other pneumatic control means which displaces telescoping mast sections between retracted and extended positions. Additionally, a pneumatically telescoping mast may include a mechanism for pivoting the mast between horizontal and vertical positions. Such an arrangement is disclosed in copending application U.S. Ser. No. 286,269, now U.S. Pat. No. 5,572,837 assigned to the assignee of the present invention. This arrangement is separate from the pneumatic control mechanism.
In many applications the pneumatic control mechanism is powered by an air compressor, connected to a DC power source and the mechanism for pivoting the mast is controlled by a DC motor located adjacent to the platform base from which the mast is raised. Alternatively, the air compressor or mechanism for pivoting the mast can be provided with power from an AC power source. However, where the telescoping mast is provided with a light source at the end, the light has been always necessarily powered by an AC power source. AC power has always been required because of the light intensity used on telescoping masts. Either a 110 volt or 220 volt power source has been required in order to provide adequate lighting intensity in which emergency personnel can work effectively.
Such an AC power source is generally run by a gasoline generator hooked to an alternator which then is attached to the light source via an electrical line. Generally speaking, the AC power source has been provided by the motor vehicle itself, though a self contained generator is possible. An AC power source generally requires that the vehicle or generator continue to run at all times to operate the light source. During an emergency situation in which the light is needed for rescue or other purposes, it is important that the generator or vehicle not run out of gas. If the gasoline supply is exhausted, the generator will shut down and the lights automatically turn off.
Two different types of AC power sources are generally used for pneumatically telescoping masts. The most typical has the power line running directly from the emergency vehicle alternator to the light source. Therefore, the emergency vehicle provides power to the light via the alternator, while the remainder of pneumatic mast functions run on DC power. The other AC power option involves providing a separate self-contained gasoline generator and alternator. However, such a unit is not typically seen since a self-contained generator and alternator would not only be redundant to the vehicle alternator, but also too heavy to be mounted on the roof of most emergency vehicles. As is well known and can be seen in the prior art, AC power requires heavy duty wiring insulation to protect against fire or electrical shock. This results in more bulk and weight added to the mast, since the wiring must be pulled up and pushed down during extension and retraction of the mast. As such, the extension and retraction mechanisms need to have a larger capacity and need to work harder than what otherwise might be required. This is especially true with variations in temperature. For instance, cold temperatures result in typical wiring insulation becoming less flexible and elastic, thereby requiring the extension and retraction mechanisms to work even harder to pull wire up the mast as the mast is being extended.
Certain systems of prior art telescoping masts already use 12 volt DC power as the preferred power source. These systems include the mechanism for pivoting the mast between horizontal and vertical positions as well as the pneumatic control mechanism. Generally these systems can run and be directly wired to the vehicle battery. However, in some cases, these same mast systems may be powered with self-contained DC power which is not connected to the vehicle at all. Thus, the pneumatic control mechanism or compressor and the mechanism for pivoting the mast typically runs on lower power than the light (12V or 24V DC as opposed to 110V or 220V AC) and indeed can be run on self-contained DC power. However, since the light must be run on AC power, the light is necessarily connected to the power generating system of the emergency vehicle at all times. Thus, the pneumatically telescoping masts are not readily transferrable to other emergency vehicles since they must be integrally connected to the AC power source of the host vehicle. The internal components of an AC system are spread out across the entire pneumatic mast. This increases manufacturing costs and time required for initial assembly. As such, the light fixture at the end of a telescoping mast powered by an AC power source is also not easily interchangeable with other types of devices which could be placed on the antenna. For instance, such devices may include transmitting or receiving antennas, location devices or signal devices. The installation of a different electrical fixture usually requires complete rewiring of the fixture, which is necessarily complicated. Even the replacement of the light is also complex and complicated. Such designs do not meet current demands of versatility and interchangability.